基于钻孔图像的结构面分布分维数计算方法

在工程实践中,对岩体结构面分布的分维数进行实测往往存在一定的难度,但是采用钻孔摄像技术既能够准确获取布设的钻孔内各项地质信息,而且形成的钻孔图像能够直观地反映钻孔中岩体结构面的特征参数,因此提出了一种基于钻孔图像的岩体结构面分布分维数计算方法。该方法的原理是:首先,通过钻孔图像获取研究区域内各钻孔内的岩体结构面的特征参数(包括倾角、倾向、隙宽、间距);然后,根据各钻孔之间的连通判断准则,判断区域内各钻孔结构面的连通性,并估算出研究区域内结构面的迹长值,同时参照钻孔的孔位及深度信息,来界定研究区域模型的范围;最后,结合Monte-Carlo法,建立岩体结构面分布的三维网络模型,根据分维数计算方法,求解模型各研究面的分形维数,并将3个钻孔的整体连通模型和各钻孔模型所得到的分维数开展对比分析。结果表明,该方法的计算结果与其他评价方法的结论一致。

Fractal dimension calculation method on rock mass structural plane distribution based on borehole image

The measure of fractal dimension of rock mass discontinuity distribution in engineering applications is difficult, and the geological information by drilling borehole camera technology can be obtained accurately. Borehole image can visually reflect the characteristics of rock mass discontinuity parameters in drilling. Therefore, the calculation method on fractal dimension of structure planes in rock mass based on borehole images was proposed in this paper. Firstly, rock structure characteristic parameters(angle, inclination, fracture width and spacing) of each borehole were obtained from the borehole images. Then, the regional connectivity of borehole structure was judged according to the connectivity criterion between boreholes, and the trace lengths of structural plane were estimated. The range of regional model was defined by considering locations and depths of boreholes. Finally, three-dimensional fractal model of structural plane distribution in rock mass was established by Monte-Carlo method, by which the fractal dimensions of structural planes of boreholes were obtained. The fractal dimensions obtained by three separated borehole models and by the integrated models were compared, it was proved that the analysis results were consistent with other evaluation methods.